The primary purpose of this contract is the purification of "virus" from various milk samples obtained from lactating women from designated high risk populations in Israel and assay for RNA-instructed DNA polymerase as well as a further attempt to grow the milk "virus" in human tissue culture cells. It is planned to collect and process breast milk samples from various Maternity Centers in Isreal and to use present techniques for purifying the virus particles as well as to work on more efficient methods for screening milk samples.